Tillage frequency affects microbial metabolic activity and short-term changes in CO 2 fluxes within 1 week in karst ecosystems

Purpose Tillage disturbance can significantly affect soil microbial metabolic activity and CO 2 fluxes. Nevertheless, the influence of different tillage frequencies on microbial metabolic activity and short-term temporal changes of CO 2 fluxes remains unclear. Materials and methods We established an in situ experiment with the following treatments: no tillage (T0), semiannual tillage (T1), tillage every 4 months (T2), bimonthly tillage (T3), and monthly tillage (T4). The microbial metabolic activity (Biolog EcoPlate), short-term (hours to days) temporal changes in CO 2 fluxes within 1 week, and soil properties were measured after 1 year of treatment. Results and discussion The highest CO 2 emissions occurred in the first 72 h after tillage treatment and were significantly higher in T3 and T4 than in T0, T1, and T2 within 1 week. Average well color development (AWCD) values reflect microbial metabolic activity and were significantly higher in the tillage treatments (T1, T2, T3, and T4) than under no tillage. There was no significant difference in the Shannon diversity index under all treatments. A higher Simpson diversity index was observed under high tillage frequency in T2, T3, and T4 compared with T0 and T1, while the highest was observed in T2. The highest utilization of carboxylic acids, amino acids, and polymers occurred in T3 and T4 soils, whereas T2 had the highest utilization of carbohydrates, amines, and miscellaneous carbon sources. AWCD values and short-term CO 2 fluxes were significantly correlated with annual changes in soil organic carbon (△SOC), annual changes in dissolved organic carbon (△DOC), microbial biomass carbon (MBC), and large macroaggregates (> 1 mm). Conclusions These results suggest that frequent tillage disturbance increases microbial metabolic activity, which can stimulate short-term CO 2 emissions through changes in soil aggregates, SOC, DOC, and MBC.